Pole parts for medium-voltage or high-voltage switchgear assemblies must have a high current carrying capacity. In this case, contact resistances are kept as low as possible. The high currents that flow in the connected state (load case) may, however, produce significant amounts of thermal energy, even when the contact resistances are low. The produced thermal energy must be dissipated in a suitable manner.
For reasons relating to dielectric hermetic sealing of such a pole part, the vacuum interrupter chambers can be composed of ceramic having a low thermal conductivity. In this arrangement, the majority of the thermal energy is dissipated out of the chamber by the supply lines (generally composed of copper material), and is concentrated in this area. The vacuum interrupter chamber is encapsulated overall in an electrically insulating encapsulation casing. The electrical insulation characteristic of the encapsulation casing can also reduce the heat transmission.